Definition
The most common zygomatico-maxillary complex (ZMC) fracture pattern involves fracture of the frontozygomatic suture (lateral orbital rim), the zygomatic arch, the lateral buttress (zygomatico-maxillary buttress), and the inferior orbital rim. The fractures through the lateral buttress and the inferior orbital rim are commonly connected by an anterior maxillary wall fracture. Although this represents the most common fracture pattern, significant variation exists. For example, the zygoma itself may be fractured into pieces, and partial ZMC fractures, involving some, but not all of the fractures listed above, may occur.

The zygomatic complex plays a key role in mid-facial contour and protection of orbital contents, and has many important relationships to surrounding soft tissue structures that influence the clinical signs of a ZMC fracture. The masseter muscle attaches to the zygoma, and its unopposed force on the mobile bone fragment after ZMC fracture is responsible for the inferior displacement and medial rotation of the malar process. This displacement is appreciated clinically as flattening of the malar eminence. The temporalis muscle inserts on the coronoid process of the mandible and travels beneath the zygomatic arch to its attachment on the temporal bone superiorly. Depressed ZMC fractures can exert pressure on the temporalis muscle, causing trismus and severe pain with mastication. The lateral canthal tendon attaches to the inner aspect of the lateral orbital rim at Whitnall’s tubercle. Inferior displacement of the zygoma after a fracture may result in displacement of the lateral canthus. Step-offs on the lateral or inferior orbital rims may often be palpated. Fractures may pass through, or close to the infraorbital foramen, resulting in anesthesia of the infraorbital nerve distribution. Significant facial edema is common, and it is important to investigate for additional maxillofacial injuries. The presence of diplopia or difficulty with eye movements may indicate extraocular muscle pathology (e.g., entrapment). Change in globe positioning, often in the form of enophthalmos, may occur.

Diagnostics
Facial fractures often occur as the result of significant trauma and evaluation should begin with airway control and homodynamic stabilization. Spinal cord injury should be ruled out. A thorough history and physical, including a complete head and neck exam, may then be performed. With any midfacial fracture, suspicion for CSF rhinorrhea and/or otorrhea should be high. ZMC fractures involve orbital wall fractures, and the eye must be completely evaluated. Examination of dental occlusion is also important, as fractures can extend through the maxillary alveolus, resulting in malocclusion. Facial radiographs, particularly the submental vertex view, may suggest the diagnosis, but maxillofacial CT scan is considered the modality of choice for diagnosis of ZMC fractures.

Prophylaxis
The use of restraints, seat belts, and protective headgear can help prevent ZMC fractures.

Therapy

ZMC fractures in which the zygoma is non-displaced and ophthalmologic examination is normal can be treated conservatively with analgesia, soft diet, and close follow up. Indications for surgical reduction and fixation of a ZMC fracture are cosmetic deformity resulting from inferior and medial displacement of the zygoma, trismus, pain with chewing, enophthalmos, diplopia, or gaze restriction. Stable surgical repair often requires fixation of at least two fracture sites, most commonly the frontozygomatic suture line and the zygomatico-maxillary buttress. Care must be taken to avoid post-operative enophthalmos, as reduction of the zygomatic fracture may accentuate an already-present orbital floor fracture, requiring orbital floor plating. Peri-operative antibiotics should be considered in patients with facial fractures. Patients with ZMC fractures that are not displaced on initial presentation should be followed closely to assure that the fracture does not become displaced with time.

ZMC fractures are the second most common mid-face fracture, after nasal fractures. 80% of ZMC fractures occur in males and 80% of ZMC fractures occur between the ages of 18-45, with peak incidence between 20-30 years of age. Assault is responsible for the majority of ZMC fractures (40%), followed by sports injuries, MVA, and falls.